Somewhere over the... what?

In order to defend his controversial claim that observation is unaided perception, Bas van Fraassen, the originator of constructive empiricism, suggested that, for all we know, the images produced by a microscope could be in a situation analogous to that of the rainbows, which are ‘images of nothing’. He added that reflections in the water, rainbows, and the like are ‘public hallucinations’, but it is not clear whether this constitutes an ontological category apart or an empty set. In this paper an argument will be put forward to the effect that rainbows can be thought of as events, that is, as part of a subcategory of entities that van Fraassen has always considered legitimate phenomena. I argue that rainbows are actually not images in the relevant (representational) sense and that there is no need to ontologically inflate the category of entities in order to account for them, which would run counter to the empiricist principle of parsimony

BPS Solutions in AdS/CFT

We study a class of exact supersymmetric solutions of type IIB Supergravity. They have an SO(4) x SU(2) x U(1) isometry and preserve generically 4 of the 32 supersymmetries of the theory. Asymptotically AdS_5 x S^5 solutions in this class are dual to 1/8 BPS chiral operators which preserve the same symmetries in the N=4 SYM theory. We analyse the solutions to these equations in a large radius asymptotic expansion: they carry charges with respect to two U(1) KK gauge fields and their mass saturates the expected BPS bound. We also show how the same formalism is suitable for the description of the AdS_5 x Y^{p,q} geometries and a class of their excitations.Comment: 5 pages, Latex, uses w-art class (included). To appear in the Proceedings of the RTN workshop "ForcesUniverse", Naples, October 9-13, 200

3D gauged supergravity from SU(2) reduction of N=1N=1 6D supergravity

We obtain Yang-Mills $SU(2)\times G$ gauged supergravity in three dimensions from $SU(2)$ group manifold reduction of (1,0) six dimensional supergravity coupled to an anti-symmetric tensor multiplet and gauge vector multiplets in the adjoint of $G$. The reduced theory is consistently truncated to $N=4$ 3D supergravity coupled to $4(1+\textrm{dim}\, G)$ bosonic and $4(1+\textrm{dim}\, G)$ fermionic propagating degrees of freedom. This is in contrast to the reduction in which there are also massive vector fields. The scalar manifold is $\mathbf{R}\times \frac{SO(3,\, \textrm{dim}\, G)}{SO(3)\times SO(\textrm{dim}\, G)}$, and there is a $SU(2)\times G$ gauge group. We then construct $N=4$ Chern-Simons $(SO(3)\ltimes \mathbf{R}^3)\times (G\ltimes \mathbf{R}^{\textrm{dim}G})$ three dimensional gauged supergravity with scalar manifold $\frac{SO(4,\,1+\textrm{dim}G)}{SO(4)\times SO(1+\textrm{dim}G)}$ and explicitly show that this theory is on-shell equivalent to the Yang-Mills $SO(3)\times G$ gauged supergravity theory obtained from the $SU(2)$ reduction, after integrating out the scalars and gauge fields corresponding to the translational symmetries $\mathbf{R}^3\times \mathbf{R}^{\textrm{dim}\, G}$.Comment: 24 pages, no figures, references added and typos correcte

Shockwaves in Supernovae: New Implications on the Diffuse Supernova Neutrino Background

We investigate shock wave effects upon the diffuse supernova neutrino background using dynamic profiles taken from hydrodynamical simulations and calculating the neutrino evolution in three flavors with the S-matrix formalism. We show that the shock wave impact is significant and introduces modifications of the relic fluxes by about $20 \%$ and of the associated event rates at the level of $10-20 \%$. Such an effect is important since it is of the same order as the rate variation introduced when different oscillation scenarios (i.e. hierarchy or $\theta_{13}$) are considered. In addition, due to the shock wave, the rates become less sensitive to collective effects, in the inverted hierarchy and when $\sin^2 2 \theta_{13}$ is between the Chooz limit and $10^{-5}$. We propose a simplified model to account for shock wave effects in future predictions.Comment: 8 pages, 9 figure

SUSY radiative corrections on mu-tau neutrino refraction including possible R-parity breaking interactions

In this paper we investigate the one-loop radiative corrections to the neutrino indices of refraction from supersymmetric models. We consider the Next-to Minimal Supersymmetric extension of the Standard Model (NMSSM) which happens to be a better supersymmetric candidate than the MSSM for both theoretical and experimental reasons. We scan the relevant SUSY parameters and identify regions in the parameter space which yield interesting values for V_{mu tau}. If R-parity is broken there are significant differences between MSSM and NMSSM contributions contrary to the R-parity conserved case. Finally, for a non-zero CP-violating phase, we show analytically that the presence of V_{mu tau} will explicitly imply CP-violation effects on the supernova electron (anti-) neutrino fluxes.Comment: 23 pages, 15 figures; v2: typos and 5 figures correcte

Another blast from the past or why the left should embrace strict legalism: a reply to Frank Carrigan

This article argues that Carrigan's criticism of Sir Owen Dixon's strict legalism provides a clear example of the preconceptions and misconceptions that blind most opponents of Dixon's method. It argues that Carrigan's examination of a series of labour law cases does not support his contention that Dixon was a covert judicial activist; that, in contrast to the close relationship between strict legalism and popular democracy, opponents of strict legalism seem far more comfortable with the politics of the reactionary past: and that strict legalism is a necessary preconditon if the common law is to act as an institutional counterweight to an unbridled market. Rather than viewing strict legalism as a misleading and misconceived way of understanding the judicial role, it should be understood as an essential precondition for the operation of the rule of law and the continued independence of the common law in an era of impoverished institutional life

On the perturbative corrections around D-string instantons

We study ${\cal F}^4$-threshold corrections in an eight dimensional S-dual pair of string theories, as a prototype of dual string vacua with sixteen supercharges. We show that the orbifold CFT description of D-string instantons gives rise to a perturbative expansion similar to the one appearing on the fundamental string side. By an explicit calculation, using the Nambu-Goto action in the static gauge, we show that the first subleading term agrees precisely on the two sides. We then give a general argument to show that the agreement extends to all orders.Comment: 12 page

AdS/CFT correspondence and D1/D5 systems in theories with 16 supercharges

We discuss spectra of $AdS_3$ supergravities, arising in the near horizon geometry of D1/D5 systems in orbifolds/orientifolds of type IIB theory with 16 supercharges. These include models studied in a recent paper (hep-th/0012118), where the group action involves also a shift along a transversal circle, as well as IIB/$\Omega I_4$, which is dual to IIB on $K3$. After appropriate assignements of the orbifold group eigenvalues and degrees to the supergravity single particle spectrum, we compute the supergravity elliptic genus and find agreement, in the expected regime of validity, with the elliptic genus obtained using U-duality map from (4,4) CFTs of U-dual backgrounds. Since this U-duality involves the exchange of KK momentum $P$ and D1 charge $N$, it allows us to test the (4,4) CFTs in the $P < N/4$ and $N < P/4$ regimes by two different supergravity duals.Comment: 28 pages, no figure